Muffler



United States Patent O MUFFLER Dan M. Finch, Berkeley, Calif.

Application July 16, 1951, Serial No. 236,876

Claims. (Cl. 181-50) This invention relates to mulers.

Prior muilers have been objectionable, particularly mulers for diesel trucks and the like, in that they have been too noisy, because these muillers, while being eiective to suppress and attenuate high frequency sound waves, readily pass low frequency sound waves such as between fty and three hundred cycles per second, which low frequency sound waves are responsible to a large extent for the objectionable noise.

It is a main object of the present invention to provide a muiiier for suppressing and attenuating there low frequency sound waves by means including an anti-resonance tube constructed to be in anti-resonance with a band of low frequency sound waves and having a maximum suppression or attenuation occurring at approximately one hundred cycles per second.

Another object of the present invention is to provide a muler as above described with an anti-resonance tube open at one end and having sound attenuation material in the opposite end to broaden the band of frequencies to which the tube is anti-resonant.

Still a further object of the present invention is to provide a mufer as above described having other sound attenuating material located to be eeictive to attenuate or suppress the low frequency energy as well as high frequency energy.

Prior mufiiers have also been objectionable in that when certain vital parts corroded or were otherwise worn out, they could not be replaced, hence, the entire muflier had to be discarded, or the parts could be replaced only by the use of special operations such as welding and/or the use of special tools, making such replacement in most instances prohibitive because of the resulting excessive expense. Also, since the entire muier normally must be discarded, it was not practical to use relatively expensive corrosion resistant material such as stainless steels, Monel metal, inconel and like materials in constructing such mutliers.

It is another object of the present invention to provide a muler in which certain vital parts thereof are formed of corrosion resistant materials, and in which construction other parts not formed of corrosion resistant material are protected by inexpensive replaceable parts, the muffler being constructed to be readily disassembled with only a few common tools, thereby permitting ready replacement of parts, thus prolonging the life of the mufller and justifying the use of relatively expensive corrosion resistant material for certain parts of the muiller.

Various other objects will be apparent from the following description taken in connection with the accompanying drawings, wherein:

Fig. 1 discloses a longitudinal section througha muier embodying the concepts of the present invention.

Fig. 2 is a vertical cross-section taken along line 2 2 of Fig. 1 showing the construction of the outlet end late. p Fig. 3 is a vertical cross-section taken along line 3 3 of Fig. 2 showing part of the clamping means for clamping the anti-resonance tube to the housing.

Fig. 4 shows, separately, and partly in section, one of the replaceable annular sound attenuating cartridges.

Fig. 5 shows, separately, and partly in section, the replaceable sound attenuating cartridge for the antiresonance tube.

Referring to the accompanying drawings, the muler disclosed, and embodying the concepts of the present 2,705,541 Patented Apr. 5, 1955 ICC 2 invention, comprises a housing generally entitled A within which is disposed an anti-resonance tube B which has a closed end adjacent the outlet end of the housing and an open end secured to the inlet end of the housing. The closed end of anti-resonance tube B is secured to the outlet end of the housing A by means of a clamping device generally entitled C. The anti-resonance tube B is perforated adjacent its operi inlet end to allow exhaust gases entering the inlet of the housing to pass through these openings for passage through the annular space between the anti-resonance tube and the housing and out through the outlet. The anti-resonance tube has a length such that it is in anti-resonance with a band of low frequency sound waves, the tube being constructed to have a maximum suppression or attenuation centered about approximately one hundred cycles per second. That is, these low frequency sound waves after entering the inlet of the housing will be reflected back from the closed end of the anti-resonance tube so that the reflected waves will be out of phase with the incoming waves, therefore at least partially suppressing or attenuating the incoming waves and therefore resulting in a definite decrease in the amplitude of these low frequency waves and consequently definitely decreasing their effectiveness to produce the objectonal noise which would otherwise result.

More particularly, the housing A of the muler includes an outer tubular shell 11 having an inlet end plate 13 disposed at the inlet end of the shell and an outlet end plate 15 disposed at the outlet end of the shell, said end plates having annular ribs 17 and 19, respectively, over which the shell 11 tits, as clearly shown in Fig. l.

Anti-resonance tube B comprises a tubular member 21 having the lefthand end thereof, as the parts are depicted in Fig. 1, which is the inlet end of the anti-resonance tube, ared at 23 and formed integrally with the inlet end plate 13. Adjacent the inlet end of tubular member 21 there are formed bands of perforations 25.

The opposite closed end of anti-resonance tube B is closed by means of a replaceable sound attenuating cartridge or plug 26 comprising a reticulated cylindrical housing 27 enclosing a mass of glass wool and silica wool 28. Cartridge 26 is held in place by means of in- Wardly extending lugs 29 formed on the interior of tubular member 21 and a cross-piece 31 forming part of the clamping device C. The cartridge or plug 26 closes the righthand end of tubular member 21, as clearly apparent from Fig. l, and is responsible for broadening the band of frequencies to which the anti-resonance tube B is anti-resonant.

The closed end of tubular member 21 is secured to the outlet end plate 15 by means of clamping device C, the cross-piece 31 of said clamping device having ends extending through apertures 33 in the side walls of tubular member 21 and having rearwardly extending lugs 35 for retaining said cross-piece in place and limiting sidewise movement thereof. The cross-piece is also provided with a raised center portion 37 which threadedly receives a rod 39, the other end of which rod is slidably received through a boss 41 provided on end plate 15. The rearward end of rod 39 is threaded to receive a nut 43, there being a washer 45 below the nut, said nut when tightened drawing the cross-piece 31 rearwardly and, therefore, clamping the shell 11 between the end plates 13 and 15. When the nut 43 is unthreaded, the shell and anti-resonance tube B can be readily disassembled by merely removing end plate 15 and shell 11.

As shown in Fig. 1, apertures 33 are suiciently large to accommodate lugs 35, when nut 43 is unthreaded and cross-piece 31 moved slightly forwardly, to permit removal of said cross-piece 31 and replacement of cartridge 26.

As is apparent by a comparison of Figs. l and 2, end plate 15 has openings 47 defined by spokes or ribs 49 connecting boss 41 to the main body portion of outlet end plate 15, openings 47 allowing the passages of exhaust gases out through the housing A.

The anti-resonance tube B is preferably formed of cast-iron which is resistant to corrosion to an extent greater than ordinary sheetmetal and steel. The tubular shell 11 can be constructed of relatively corrosive material such as sheetmetal or steel.

In the inlet end of shell 11, there is disposed a stainless steel tubular heat shield 51. The lefthand end of said shield fits within the annular rib 17 of end plate 13 and the opposite end has an inwardly extending flange 53 abutting against the forwardmost cartridge of a plurality of annular sound attenuating cartridges 55 which line the interior of shell 11 from the righthand end of the heat shield, as the parts are depicted in Fig. 1, to the end plate 15. The righthand or rearwardmost annular cartridge engages rib 19 of outlet end plate 15. The longitudinal dimensions of shield 51 and cartridges 55 are such that when the shell 11 is clamped between end plates 13 and 15, the annular cartridges are slightly compressed to firmly hold them and shield 51 in position. The external diameter of shield 51 is sufciently smaller than the internal diameter of shell 11 to provide a dead air space 56 for insulating the forward end of shell 11 from the heat of the incoming exhaust gases.

There is a suitable inlet pipe adapter 57, for the inlet end of housing A, secured to inlet end plate 13 by screws 59, and similarly for the outlet end of the housing there is a suitable outlet pipe adapter 61 secured to the outlet end plate by screws 63, said adapters fitting sections of the exhaust pipe and being replaceable to permit the muiier to tit different sizes of exhaust pipes.

Each of the annular sound attenuating cartridges 55 is of identical construction and includes a reticulated spool-shaped support 71 about which is formed a layer of glass wool and silica wool 73 effectively filling the spool. The diameters of the cartridges 27 for the antiresonance tube B and 55 for the shell A are, of course, such as to enable said cartridges to be readily inserted in and removed from their positions to enable replacement thereof.

As is apparent from Fig. l, the inner diameter of each cartridge 55 is greater than the external diameter of antiresonance tube B, by an amount to provide an annular space 75 between the cartridges and anti-resonance tube B for the passage of exhaust gases through the muffler. As is best shown in Fig. 1, the inwardly extending flange 53 of heat shield 51 likewise terminates short of the exterior of anti-resonance tube B by an amount to allow for the passage of gases along the exterior of anti-resonance tube B. m..

The operation of the mutiler is as follows: Exhaust gases entering through adapter 57 are reected from the closed end of anti-resonance tube B, said tube being of such length that the reflected low frequency sound waves will be approximately 180 out of phase with low frequency waves entering the anti-resonance tube, therefore effectively suppressing and to a large extent cancelling the energy of the incoming waves and therefore eliminating a major portion of the objectionable noise normally issuing from muillers. The gases pass through the perforations in anti-resonance tube B and down through the annular space between the cartridges 55 and the exterior of anti-resonance tube B and out through the openings 47 in the end plate 15.

The stainless steel heat shield 51 is effective to reect the radiant heat of the exhaust gases, and annular dead air space 56 between the heat shield and the shell 11, insulates the inlet end of shell 11 to thereby prolong the life thereof.

lf after a period of use, it is determined that the cartridges 55 or 26 need to be replaced, this can be readily accomplished by unthreading nut 43, removing outlet cnd plate 15 and then removing the cartridges 55 and replacing the cartridges which are in need of replacement. Cartridge Z6 can also be readily removed and replaced when desired by a suitable manipulation of rod 39 and cross piece 31. Although heat shield 51 in combination with the annular sound attenuating cartridges 55 protects the shell 11 against corrosion, eventually the shell may corrode. When such occurs, shell 11 can be readily replaced as before explained. Likewise, if after a period of use the cast iron anti-resonance tube B is in need of replacement, it can likewise be replaced.

lt is pointed out that the sound attenuating cartridges 55 are effective to not only further suppress and attenuate low frequency sound waves passing from one end of the housing to the other, but also are effective to suppress and attenuate low energy but objectionable high frequency sound waves up to a point of approximately three thousand cycles per second.

By the present invention, a muller has been provided having an anti-resonance tube effective to suppress and attenuate high energy low frequency sound waves and, therefore, eliminate a major portion of the objectionable noise usually found in mullers, particularly mufflers for diesel trucks and the like. By the provision of a sound attenuating cartridge in the anti-resonance tube, the antiresonance characteristics of the tube are broadened to include a wider band of low frequencies. The annular cartridges 55 are effective to further suppress both low frequency and high frequency sound waves and to line and protect the shell 11. The muffler of the present invention is also constructed so it may be readily disassembled and assembled with the use of only a few common tools, permitting the parts thereof to be readily replaced when desired, therefore prolonging the life of the muffler and justifying the use of relatively expensive non-corrosive metals.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

l. A muffler, comprising an outer tubular shell having an inlet end and an outlet end, removable end plates abutting the ends of the shell, a removable anti-resonance tube in the shell having an open end adjacent the inlet end of the shell, perforations in said anti-resonance tube adjacent the open end thereof, and means including a releasable clamp for securing said tube to said end plates to clamp the shell between said end plates and permit replacement of the parts upon release of the clamp and sound attenuation annular cartridges lining a portion of the interior of the shell spaced from said anti-resonance tube and removable upon removal of the end plates to permit replacement of said cartridges.

2. A muler, comprising an outer tubular shell having an inlet end and an outlet end, removable end plates abutting the ends of the shell, a removable anti-resonance tube in the shell having an open end secured to the end plate at the inlet end of the shell, perforations in said anti-resonance tube adjacent the open end thereof, and releasable clamping means securing the opposite end of the tube to the other end plate to clamp the shell between the end plates, and sound attenuation annular cartridges lining a portion of the interior of the shell spaced from said anti-resonance tube and removable upon removal of the end plates to permit replacement of said cartridges.

3. A mufller, comprising an outer tubular shell having an inlet end and an outlet end, removable end plates abutting the ends of the shell, a removable anti-resonance tube in the shell having an open end secured to the end plate at the inlet end of the shell, perforations in said anti-resonance tube adjacent the open end thereof, and releasable clamping means securing the opposite end of the tube to the other end plate to clamp the shell between the end plates and a removable sound attenuation plug in said opposite end of the tube, and replaceable sound attenuation annular cartridges spaced from said antiresonance tube and adjacent said shell.

4. A muffler, comprising an outer tubular shell having an inlet end and an outlet end, removable end plates abutting the ends of the shell, a removable anti-resonance tube in the shell having perforations formed therein adjacent one end thereof and having said end secured to the inlet plate at the inlet end of the shell, said one end being open, a removable stainless steel heat shield abutting the last mentioned end plate, sound attenuation annular cartridges lining the interior of the shell between the shield and the other end plate, and releasable clamping means securing the opposite end of the tube to the other end plate to clamp the shell between the end plates and retain the cartridges and heat shield in position.

5. A muffler, comprising an outer tubular shell having an inlet end and an outlet end, an anti-resonance tube suspended within the shell and having its side walls spaced from the side walls of the shell, said anti-resonance tube having an open end in communication with the inlet of the shell and having its opposite end closed by a flat wall arranged perpendicular to the longitudinal axis of the tube, said anti-resonance tube having openings in the side wall thereof only adjacent the open end thereof to permit the passage of exhaust gases from the antiresonance tube into the space between the housing and tube, sound attenuating means disposed in the space between the tube and housing, and sound attennating 1,811,762 Schnell June 23, 1931 means disposed in the closed end of the tube and exposed 1,995,071 MacKenzie Mar. 19, 1935 to the interior of the tube to broaden the range of fre- 2,096,260 Pavillon Oct. 19, 1937 quencies to which the tube is anti-resonant. 2,138,510 Rauen Nov. 29, 1938 5 2,373,231 Demuth Apr. 10, 1945 References Cited in the file of this patent 2,523,260 Campbell Sept. 26, 1950 Walker NOV. 24,

821,828 Phelps May 29, 1906 FOREIGN PATENTS 844,669 Fairchild Feb. 19, 1907 10 563,018 Germany Feb. 23, 1930 1,766,945 Riehm June 24, 1930 487,816 Great Britain June 27. 1938 

